User operated drug delivery devices are as such known in the prior art. They are typically applicable in circumstances, in which persons without formal medical training, i.e., patients, need to administer an accurate and predefined dose of a medicinal product, such as heparin or insulin. In particular, such devices have application, where medicinal product is administered on an irregular basis over a short term or long-term period.
In order to accommodate with these demands, such devices have to fulfil a number of requirements. First of all, the device must be robust in construction, yet easy to use in terms of handling and in understanding by the user of its operation and the delivery of the required dose or medicament. The dose setting or selecting must be easy and unambiguous. Where the device is to be disposable rather than reusable, the device should be cheap to manufacture and easy to dispose (preferably being suitable for recycling). To meet these requirements, the number of parts required to assemble the device and the number of material types the device is made from should be kept at a minimum.
For instance, US 2007/0088290 A1 discloses a drive device for advancing an advancing element relative to a housing over an entire advancing distance. Here, an ampule is connected to a housing of the drive device and a plunger is connected to the advancing element, such that the tensioning force or pressure force of a spring device is transmitted to the plunger. The plunger in the ampule is advanced toward the outlet, leading to a dispensing of the product contained in the ampule. After the advancing element has been advanced by a partial advancing distance, the spring device is tensioned again, i.e. re-tensioned.
After the device has been actuated, the plunger is driven in longitudinal direction exclusively by the spring element. In this way, the movement of the advancing element or the plunger is totally decoupled from the push button and all other components of the device the user may interact with. Hence, during an advancing motion the user or patient has no possibility to manipulate the dose injection process. In particular, when the dose to be injected comprises a multitude of dosing units, after having actuated the device, the entire preselected amount of medicinal product is automatically dispensed, which may in some cases lead to discomfort.
It is therefore an object of the present invention to provide an improved drug delivery device for dispensing of a medicinal product, for example a device which provides a user-controlled dispensing even during the process of dose dispensing. Further, a drug delivery device having a reduced number of components and being easy to handle may be provided, which device may provide intuitive and unambiguous dose selecting and dose dispensing.